Inland Waterways

Dans le document The Economic Cost of Invasive Non-Native Species on Great Britain (Page 110-115)

Waterways are crucial for tourism and recreation and they are estimated to provide over

£500 million of public benefit annually, as well as over £1 billion in income to local economies54. Over 13 million people made over 380 million visits to the waterways in 2009.

The various effects of INNS on recreational activities carried out using inland waterways range from direct effects, such as the presence of mats of floating weeds, such as floating pennywort, that may restrict navigation or prevent angling, to more indirect effects, such as riparian weeds that may hinder access to the water and loss of open surface water by continuous mats giving rise to aesthetic and safety issues. The rooted invasive aquatic species can also cause flood risks by restricting water flows and blocking weirs and sluices.

Furthermore, a number of species, such as Japanese knotweed, Chinese mitten crab and zebra mussels, can cause damage to waterway infrastructure and may interfere with water control structures, potentially posing a further flood risk. In addition, many aquatic INNS are very mobile and may affect water quality and biological diversity, reducing the aesthetic value of the waterways causing a decline in their recreational value, potentially affecting local economies that are reliant on recreation and tourism.

9.3.1 Angling

A wide range of INNS, including fish, riparian weeds, crustaceans and aquatic plants can affect angling. Each of these taxa includes species that can have a serious impact on the willingness or ability of anglers to fish a stretch of water though the period over which these effects can be felt can vary significantly between taxa, as can the length of time required for any treatment programme. The angling industry makes a significant contribution to the UK economy. There are an estimated 2.9 million anglers in England and Wales and each angler spends an estimated £1483 per year on such items as travel, food and drink, bait, tackle and permits (£1,000 per year per angler in 1994: National Rivers Authority 1995), giving a total estimated value of angling to the economy of these two countries of approximately £4.3 billion. The angler spend in Scotland was estimated at £112.5 million in 2004. A further

£164.6 million contribution to Scottish output from angling, and £77.1 million in household income due to angling as well as the 4,418 jobs in the sector, worth £125 million, can be

54 BW annual report 2010

added to this spending figure (from Radford et al. 2004). This gives a total value of angling to Scotland of £479.2 million in 2004 or £548.5 million today. This gives a total estimated value of angling to Great Britain of £4.85 billion.

There are 42,123 km of rivers and 1,653 lakes in England and Wales of which 26,000 km of river and 30,000 km of still waters are fished (Lyons et al. 2002). Given the annual value of fishing in England and Wales of £4.3 billion, the value of angling on each kilometre of river is

£76,786 p.a. The spending will vary throughout the year, and will be concentrated in the summer months. Therefore if it is assumed that two thirds of fishing is carried out in this period, then a kilometre of river/lake bank in a single summer month is worth £8,532.

The key weed species that need to be considered are the water weeds, water fern (Azolla filiculoides), Australian swamp stonecrop (Crassula helmsii), floating pennywort (Hydrocotyle ranunculoides), Canadian and Nuttall’s pond weed (Elodea canadensis and E. nuttallii), curly waterweed (Lagarosiphon major) and parrots feather (Myriophyllum aquaticum), as well as the riparian species, Japanese knotweed (Fallopia japonica), Himalayan balsam (Impatiens glandulifera) and giant hogweed (Heracleum mantegazzianum). It is assumed that each of these ten main weed INNS that cause problems for anglers do so on around 10 km of river or lakeside for two summer months per year. Then based on a cost per kilometre of £8,532, each INNS would cost angling £170,636 for the 10 km stretch affected. This gives a total estimate of £1,365,084 per annum, which can be divided up using the proportion of river and canal length in each country to a cost in England of £1,177,452 and Wales, £187,632.

When the effect of crustaceans (e.g. Chinese mitten crab (Eriocheir sinensis), signal crayfish (Pacifasticus leniusculus), and the fish, topmouth gudgeon (Pseudorasbora parva) are considered, it is recognised that these can have an influence over a much longer stretch of fishable water, or often a whole catchment for a longer period than that of INNS weed species. The arrival of signal crayfish, which are known to predate heavily on fish ova, plant life and invertebrates, is often accompanied by a reduction in fish stocks and anglers ceasing to fish the affected stretches of river. In these cases it is therefore assumed that the range affected is 20 km and the impact is over a 2.5 month period giving additional figures of

£1,103,862 for England and £175,905 for Wales. Whilst all species do not affect angling to the same degree, the impacts were assumed to average out across the ten plant species and three crustacean and vertebrate species.

Scotland does not have the same system as England and without a rod licence system, it is impossible to know how many anglers are active each year. However, accurate catch data

are recorded and in 2009, on the Tweed alone, more than 12,000 salmon and grilse were caught alongside more than 4,000 sea trout which contributed to the total 85,859 salmon landed in Scotland as a whole. For comparison, the EA/CEFAS Annual Assessment of salmon stocks stated that the total rod catch for England and Wales was only 15,200.

In the absence of good information on the length of areas fished it is possible to extrapolate the figures estimated for England and Wales to Scotland based on land area. However, when the percentage value lost in England and Wales is then extrapolated to angling in Scotland, with its total value of £548.5 million, then the annual cost of both weed and crustacean INNS to angling is estimated at £239,423 for Scotland. This figure is clearly extremely low and does not adequately reflect the very high value placed on Scottish inland fishing including the very valuable salmon beats, which can cost £1,000 per rod per day in peak season and which are equally vulnerable to INNS.

It is possible to place a capital value on some stretches of river and even the value of a single fish. A typical 4-rod beat with an annual average catch of 100-150 salmon would cost an estimated £1,039,000 to purchase, including the value per fish of £7,500 (Rettie, 2010) Thus there is considerable capital value that is threatened by INNS in Scotland and these impacts can be felt over a much longer fishing season than in England and Wales.

According to a Government statement in 2008, the value of salmon fishing to Scotland is

£120,000,000 p.a. (quoted by Association of Salmon Fisheries Board, 201055) and there are on average 545,000 salmon fishing days each year. This gives a value of around £220 per day for salmon fishing. If the season is assumed to be 9 months long and the impact of all invasive species is felt over 25 km with a reduction from 5 to 4 anglers per km per day then the annual cost is £1,506,880. We also assumed that the capital value of the stretch has been reduced by at least 10% so with 25 beats (based on 2 km per beat) the loss in capital value is around £2,597,500. However, this reduction in capital value will not all be experienced in a single year, and in addition may return to previous levels if the INNS are cleared and removed, and therefore the loss of capital value is spread over 10 years giving an annual cost of £259,750. The impact of INNS of salmon fishing due to the reduction in number of anglers and the capital value of the beat is therefore £1,766,630. Due to the high value of many of its waterways, this cost of INNS to salmon fishing in Scotland was added to the main cost of £239,423 calculated above, which gives a total cost of £2,006,053.


There are also the control costs being incurred as part of the INNS management on and beside rivers in Scotland, which include two SEPA funded INNS weed control projects over 5 years valued at over 800,000 and a 3-year RAFTS Biosecurity Planning Programme for weed control valued at more than £250,000 (C. Sinclair, pers. comm.). The additional control costs identified and of direct impact on fisheries and angling are therefore £243,333 p.a.

There may be further costs, for instance related to signal crayfish that have invaded at least 50 km of salmon river in Scotland so far (C. Sinclair pers. comm.). The actual impacts may vary from complete displacement of angling activity to little impact, but the perceived impacts can result in a significant devaluation through altered anglers’ attitudes. In addition there are costs associated with the effect of signal crayfish on the food chain due to damage to aquatic plants that support the invertebrates that form part of both the signal crayfish and fish diets. These effects can have a negative impact both on fish growth rates and their population potential. However, no data could be found to quantify this effect in economic terms and therefore no additional cost is included here.

The total costs of INNS to angling is £4,894,237 of which Scotland incurs £2,249,386, England incurs £2,281,314 and Wales £363,537

9.3.2 Re cre a tiona l boa ting

There are 380 million day visitors a year to canals and rivers and the canals and rivers are used by approximately 88,000 boats (AINA 2008). The IWAC report estimates direct boating expenditure for Britain of between £200 and £400 million and that the Broads boat-hire industry is worth around £146 million p.a. In total, estimated tourism spend on inland waterways is £1.8-2.2 billion and, as calculated in the species examples, this gives a per km value of £22,553. British Waterways spent £6.8 million on vegetation management in 200956

56 BW annual report 2010.

on the 2200 miles of canal and river navigation. A significant portion of this was used to target invasive species and we estimated that over £1.5m is spent on INNS per year. The canals are primarily used for recreation and we therefore estimate that 90% of this cost is attributable to tourism and recreation (80%, 10% and 10% of that 90% in England, Scotland and Wales respectively). This may be spent on the control of floating pennywort (Hydrocotyle ranunculoides), which can make canals inaccessible, and weeds, such as giant hogweed (Heracleum mantegazzianum) or Himalayan balsam (Impatiens glandulifera).

It is assumed that the majority of the costs associated with owning and maintaining a boat, i.e. the direct costs mentioned above, would remain largely unaffected by INNS. The costs of floating pennywort to recreational boat-based tourism have been considered in the species example and the only other species that could significantly affect recreational boating are Elodea /Lagarosiphon spp. Based on the distribution of these species in the country57 and the length of waterways in each country, but in the absence of any firm data concerning how often they block waterways to a sufficient extent to impede boating, we assume that Canadian pond weed affects 20 km of waterways, and curly water weed affects only 10 km.. If it is assumed that these species only cause problems for boating for one month of the year before the weeds are cleared, and that two thirds of the season takes place over the 6 months of finer weather, then the value of one km of water in such a month is £30,071 per km. This gives a cost for Great Britain of £4,510,650, which, when combined with the costs associated with floating pennywort, gives a figure of £29,862,650 (Table 9.2).

Table 9.2. Calculation of cost of INNS to recreational boating.

England Wales Scotland

Rivers and canals (km) 33,828 4,603 50,250

Distribution of waterways affected by both species

15 2 13

Value / km (£) £22,553 £22,553 £22,553

Two thirds of value £15,035 £15,035 £15,035

Value per summer km (two thirds in 6 months) £30,071 £30,071 £30,071 Value of infected kms per summer month £451,065 £60,142 £390,923 If blocked then effect on boating extends at

least 5 times the length of infestation

£2,255,325 £300,710 £1,954,615

Floating Pennywort £25,283,000 £69,000 -

Total £27,538,325 £369,710 £1,954,615

In addition, there are the costs of fouling of access paths, slipways and pontoons by non-native bird species, such as Canada geese. The estimated costs for such cleanups are

£750 p.a. for inland sailing clubs and £2,500 for inland marinas (J Johnston, pers. comm.).

There are 450 inland sailing clubs and 102 inland marinas in England giving costs of

£337,500 and £255,000 respectively. Scotland has 15 sailing clubs and two marinas giving costs of £11,250 and £5,000 respectively and Wales has 12 inland sailing clubs, but no inland marinas, with a cost of £9,000 per annum.


Thus, the total cost to recreational boating caused by the presence of INNS in Great Britain is £30,451,000 per annum (England £28,101,000, Scotland £1,971,000 and Wales


9.3.3 Wa te rwa y ma na ge me nt cos ts

In addition to the cost incurred by angling and recreational boating due to the presence of water weeds, general control measures are undertaken by agencies, such as internal drainage boards, British Waterways and the Environment Agency, as part of general river and canal management and flood prevention measures. Oreska and Aldridge (2010) calculated that control costs for seven freshwater invasive non-native plant species amounted to at least £18.9 million per year. However, this estimate included costs incurred by, for example, boat yards, the water industry and fisheries. The cost of managing floating pennywort in rivers and canals has been calculated at £1.93 million (species example), excluding the effect on angling and boating, etc., which was calculated separately. Given the findings of the GB non-native risk assessment for most of the aquatic plant species it is reasonable to assume that the other main freshwater weed species (Australian swamp stonecrop (Crassula helmsii), water fern (Azolla filiculoides), both pond weed (Elodea canadensis and E. nuttallii), parrot’s feather (Myriophyllum aquaticum), curly water weed (Lagarosiphon major)) have a similar impact to floating pennywort. However the distribution of the species does vary58, with Canadian pond weed having the most extensive distribution, and the other species having more widespread distributions that floating pennywort, though not as widespread as Canadian pond weed. Therefore based on the £1.93 million cost estimated for floating pennywort, we estimate that control costs for Australian swamp stonecrop, water fern, parrot’s feather and curly water weed are £3 million each per annum, Nuttall’s pond weed is estimated at £4 million and Canadian pond weed control costs £5 million per annum, giving a total cost of £21.86 million. This is slightly more than Oreska and Aldridge’s figure (2010), but still seems a reasonable estimate of the cost of INNS on waterway management.

Dans le document The Economic Cost of Invasive Non-Native Species on Great Britain (Page 110-115)